A comprehensive report has been submitted by the Southwest Oncology Group Headquarters. This Group is evaluating the effectiveness of chemotherapeutic agents in three phases: Phase I studies evaluate new agents and/or treatment regimens as to pharmacologic effects; Phase II studies permit evaluation of the anti-leukemic or anti-neoplastic effect of new agents and/or treatment regimens: Phase III studies compare experimental therapeutic regimens which are effective with standard regimens. Under investigation in Phase I trials is a study to establish maximum tolerated doses of methotrexate and cytosine arabinoside when used together or within 48 hours of each other in acute leukemia. Drugs in Phase II studies are: cystosine arabinoside (synchronization in AML), adriamycin, azacytidine, busulfan, procarbazine, azapicyl, 5- fluorouracil, vincristine, CCNU, guanazole, TIC mustard, cis-platinum, ICREF 159 and methyl CCNU; and combinations of adriamycin with DIC, 5- fluorouracil with methyl CCNU, and vinca alkaloids with bleomycin. Other studies include: combination chemotherapy in acute leukemia, and adjunctive therapy in localized Ewing's osteogenic and soft tissue sarcomas. Phase III studies evaluate optimal therapy regimens for various leukemias, central nervous system leukemia, histiocytosis X, Hodgkin's disease, and non-Hodgkin's lymphomas. National and inter- group studies in Wilms' tumor, Ewing's sarcoma, and rhabdomyosarcoma are also in progress.